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astroengine writes "In a recent presentation, Kepler co-investigator Dimitar Sasselov unexpectedly announced news that the Kepler Space Telescope has discovered scores of candidate Earth-like exoplanets. Not waiting for the official NASA press release to announce the discovery, Sasselov went into some detail at the TEDGlobal talk in Oxford, UK earlier this month. This surprise announcement comes hot on the heels of controversy that erupted last month when the Kepler team said they were withholding data on 400 exoplanet candidates until February 2011. In light of this, Sasselov's unofficial announcement has already caused a stir. Keith Cowing, of NASAWatch.com, has commented on this surprise turn of events, saying it is really annoying 'that the Kepler folks were complaining about releasing information since they wanted more time to analyze it before making any announcements. And then the project's Co-I goes off and spills the beans before an exclusive audience — offshore. We only find out about it when the video gets quietly posted weeks later.' Although Sasselov could have handled the announcement better (and waited until NASA made the official announcement), this has the potential to be one of the biggest astronomical discoveries of our time — so long as these Earth-like 'candidates' are confirmed by further study."

The Star Trek classification system would indeed be far better than the whole "What's a planet" argument definitions we've had (which has been hard enough with just our solar system), and things like Dwarf planets etc. We have classes for stars, so why not planets...

Wrong. Kepler only sees close in earth sized planets, with almost no exceptions. Even though it's looking at the same area over a long time.

The reason for this is that for Kepler to see a transit of an earth sized planet, said planet has to occult the star; which in turn means that the planet's orbit has to lie on a plane defined by us and the target star, within a margin of error defined by the planet's diameter against the cone defined by the star a

Sure, the probability or transit decreases with greater orbital periods

...yes, and with the orbital angle of the planet in question -- out of an entirely rotated set of orbital possibilities, only a few intercept the path to the telescope; and the further out the planet is, the less chance. That's why the close in ones are easy, and the ones in earthlike orbits are not.

Now you'd want to replace descriptive and flexible monikers with rigid symbol classifications?OK, so perhaps, maybe, you're used to Star Trek fantasy setting, which also nicely covers most of the latin alphabet...but here, let me show you how it would look in practice:

Class (put in one symbol from this alphabet [wikipedia.org],;/. & unicode...) PlanetClass (put several, if some body is like that) Planet

And you know, the best would be to just settle with what a planet was for Greeks - that includes the Moon and the Sun... - but with Star Trek classification system.

Why does it have to be a subset of the term "just planet"? Why not try to take the Sun under pure "class" system? (Sun was a planet once, as was the Moon)

It's not bad as it is - bodies which are very much closer to "just planet" than most of the debris, but not fullfilling certain major orbital & origin criteria (and hence not swarming lists of planets, with their numbers, in the future)

Might not be a bad idea, but we're scarcely ready to tackle the task. We're starting with a sample-size of 9, (or is that 8?) with direct, personal, and extensive observation of only 1, fairly extensive robot observation of 1 more, somewhat less robot observation of 2 more, and some robot and telescopic observation of the rest. Then we get into those pesky "moons", some of which might well be considered "planets" if they orbited the sun instead of some planet. (Think Pandora, for a fictional extreme exam

I agree.
Water presence? Temperature within habitable range? At least a primordial atmosphere?
Not sure if Kepler is the right tool to collect that kind of data, but to call them "earth like" seems premature. Granted, if the size approaches that of earth chances are they're rocky, solid planets, but that's it.

It was my impression that when researchers called something "earth like" they were referring to a relatively small planet with a rocky core. By that definition both Venus and Mars are Earth-like even if, on the whole they are considerably different than Earth.

It was my impression that when researchers called something "earth like" they were referring to a relatively small planet with a rocky core. By that definition both Venus and Mars are Earth-like even if, on the whole they are considerably different than Earth.

As far as rocky core planets go, wouldn't Earth be a rather large one? I'm curious to see where the tipping point from rocky core to gas giant is, since there doesn't seem to be much middle ground.

"how large can a rocky planet be before it has a significant atmosphere?"

Depends on its initial orbit, final orbit, and the cloud it condensed out of. Too close to its star and the gasses get blown off, too far away and they freeze out. Too little iron and the magnetic field is too week to protect it from the solar wind. Too much hydrogen and not enough other gasses and it escapes to space. Too few comets in the cloud and it never accumulates enough water for reflective clouds.

I agree. Water presence? Temperature within habitable range? At least a primordial atmosphere? Not sure if Kepler is the right tool to collect that kind of data, but to call them "earth like" seems premature.

Exoplanet spectroscopy has been done, but is a very new science and extremely difficult. And first, we have to be looking at a specific planet with specific instruments.

Kepler, on the other hand, is continuously monitoring a region of the sky and some hundreds of thousands of stars for signs of planet

Isn't our solar system's ecliptic plane closely aligned with the galactic plane?That's what I remember from the last time I actually looked at the Milky Way up in the sky, anyway.

No, it's actually close to perpendicular. Earth is tilted relative about 30 degrees to the solar ecliptic, still well off the galactic plane. That's why the Milky Way kinda goes diagonally in the sky, and the planets usually don't appear in it.

I had always assumed this was for the same reason that the plane of rotation of most of

Indeed. It's very promising that as soon as we are capable of detecting a new class of planet, we do, and lots of em. Even outside of Kepler. I would think the prevailing prediction at this point would be that planetary systems and planets are common, and we are likely going to discover many planets in the habitable zones of their stars.

The nice thing though is that we only have to wait a couple years to actually know. Which is why I think we s

You can be sure that the mainstream media will fail to make the distinction between "Earth-size" and the more vaguely-defined (but more comprehensive sounding) "Earth-like". These planets are "Earth-like" in the same sense that noxious, caustic, stifling, lung-crushing Venus is "Earth-like"... if that.

Let us have our fun. There are many rocks of a size, and we didn't know that before.

Hey, I think earth-size is plenty exciting without having to say earth-like. Personally I think earth-like should at least imply in the habitable zone. Which is what the Kepler mission was specifically designed to be able to find, so I see no need to jump the gun when just finding so many exoplanets is itself a great discovery.

We're 1 year and four months into a 3 1/2 year mission. When you consider that such planets happe

Yeah seriously, and even if they have life on any of these "Earth-like" planets, how many have advanced to our level of sophistication? Without pro-wrestling, advanced snack-cake technology, and those "one quick tip to lose weight" ads on the internet, they have most definitely not achieved "Earth-like" status.

It's great that we can now detect Earth-sized planets, but it's starting to look like Jovian moons are a more common life-friendly environment. In our solar system alone there are three, possibly four moons of Jupiter and Saturn that may be able to support life.

Since the moons get most of their heat from the gravitational pull of their planets rather than from their star, they aren't dependent on getting lucky in the narrow "Goldilocks Zone" of a system.

Title of TFA: Kepler Scientist: 'Galaxy is Rich in Earth-Like Planets'
It did not say "Galaxy rich in candidates for Earth-like planets" or the more realistic "Scientists discover Earth-size planets." You can't focus on the parts of TFA that are correct and ignore the parts that are sensationalized. Too often writers take good information and add in their own nonsense. There's a difference between saying "journalist is a candidate for being an asshat" and "journalist is a proven asshat."

If data shows that the number of planets which could support life like ours is high then another factor must be pushed down, because we aren't getting any visitors, and we aren't getting any communications from other species. My bet is that the vast majority of those planets have run away from having a habitual environment by turning into planets like Venus or Mars. We are lucky that our CO2 is locked up in limestone, not free in the atmosphere.

I read before somewhere that any planets with an atmosphere similar to ours would be likely covered in water. I think we're meant to have lost a lot of our water or potential water in the same event that created the moon (ie huge asteroid kicking a whole lot of crap into orbit)? Sorry if that's completely wrong, can't remember the details but hopefully someone more knowledgeable will pipe up.

If there is no faster then light method of travelling possible, then there are unlikely to be any visitors ever. End of story.

And while 400 planets sounds like a lot, in the milky way it isn't much at all, especially if you consider the short timespan that humans have been capable of even seeing into deep space let alone make their presence known. And there are countless disasters that can wipe out a civilization.

And while 400 planets sounds like a lot, in the milky way it isn't much at all, especially if you consider the short timespan that humans have been capable of even seeing into deep space let alone make their presence known. And there are countless disasters that can wipe out a civilization.

It's not 400 planets in the galaxy. It's 400 out of 700 planets they've looked at. That implies 4/7ths of the planets in the galaxy are "Earth sized."

Interestingly, this matches up with what we have in our own Solar Syst

On top of it, the only mode of interstellar travel which seems feasible, with a technology that's almost certainly within the range of advanced civilization - embryo colonisation - would strongly promote ignoring systems where there is another civilization already; maybe even ignoring those with highly developed biosphere.

And we're shifting pretty quickly to methods of radio communication which look more and more like noise, nvm getting weaker and weaker in regards to transmission power...

I think there are more possibilities than FTL travel, just not that we'd see. There are realistic propulsion systems for non-FTL craft that could reach other stars in a few thousand years. Damn long time, right? Well, consider that we have mayflies that live less than a day. If they could live to be 100 years like us, that'd be almost forever. Who is to say we can't find ways to become not 130 or 150 years old but many thousands of years old? The universe got time, it's billions of years old and will be goo

I've found that money is over rated, and most women don't want intelligence in a man. I'm middle class, the woman I was seeing recently had just divorced her rich husband. Meanwhile, my ex-wife left me eight years ago for an unemployed auto mechanic.

Most women like "bad boys" and they all love a sense of humor and a smile. Grow a goatee and leave a stubble on your cheeks, and let your wit show but hide your intelligence. yes, there are gold diggers out there, but you have to realize they're whores; just a t

My bet is that the vast majority of those planets have run away from having a habitual environment by turning into planets like Venus or Mars.

I'm wondering how close to Earth's size a planet has to be to be an "Earth sized" planet. Venus is an Earth sized planet, and as you say, is in no way habitable. Mars isn't that much smaller, but has little atmosphere and no magnetic field; I don't see how life could exist on a planet without a magnetic field to keep stellar radiation out.

There are a whole lot more variables than size to consider.

we aren't getting any visitors

Maybe Doctor Fielgud [slashdot.org] and his colleagues will figure out that a "moon sized double planetoid" can harbor life if it has an iron core, and that oxygen isn't a poison to all species. And maybe the NASA people will start looking at satellites of gas giants around other stars. Meanwhile, that bit of fiction I linked gives a possible explanation as to why nobody's calling. Here's another bit of fiction [baetzler.de] with an alternative suggestion.

Magnetic field is in large part about keeping the atmosphere from being blown away by stellar wind, not radiation per se - magnetosphere doesn't stop electromagnetic waves, and as for particle radiation - the atmosphere would stop most of it.

Anyway, it could be that Earht itself is a borderline planet for life [harvard.edu], just big enough for plate tectonics (something which Venus lacks, and which probably contributed greatly to its conditions); maybe even slightly too small in itself, but was pushed into habitable ran

Well, as far as we can tell now - they don't have plate tectonics (maybe Europa, in a way...); they are geologically active, sure, but not with plate tectonics. And that activity isn't a function of their size, but tidal forces.

The tidal forces on these moons drive the plate tectonics by keeping the core molten. So the restriction is based on "orbiting a star". Then the planet needs to be a certain size to stay volcanically active. However last I heard. The Jury was still out on why Venus has no plate tectonics.

Anyway, it could be that Earht itself is a borderline planet for life [harvard.edu], just big enough for plate tectonics (something which Venus lacks, and which probably contributed greatly to its conditions); maybe even slightly too small in itself, but was pushed into habitable range by the collision with Theia (the collision that spawned the Moon)

If you look at Earth objectively, we could be living on what so many sci-fi stories like to use as examples of 'prison' planets. Highly hostile worlds which se

You're missing one important possible reason - while habitable planets and indeed life might be common (hey, there are over a dozen suspect bodies only in our system), the conditions for complex multicellular life and very complex, competitve ecosystems (possibly promoting intelligence at some point) might be not.

How many billion yers before Earth spawned a moderately intelligent species? How many millenia before that species had even rudimentary technical civilization?

If data shows that the number of planets which could support life like ours is high then another factor must be pushed down, because we aren't getting any visitors, and we aren't getting any communications from other species...

...that we know of. I know it sounds kind of tinfoil-hatty, but it is not unreasonable to think that if ET's were visiting this planet, they might try to keep themselves hidden, so as not to alarm anyone. I would also think that if they had made contact, say with a government, that government might keep it a secret as well (see sig for more insight). Governments aren't the most forthcoming institutions these days, their military and intelligence operations even less so.

There's a version of this that uses much less tinfoil. If ETs were visiting every ten or twenty thousand years on average but didn't leave any large-scale, durable evidence behind, we wouldn't know about it. There could be dozens of robotic probes scattered around the solar system, but unless they were huge, obviously artificial or actively broadcasting we'd think they were meteoroids or small asteroids.

I'm not suggesting this is true, but merely that with the time and distance scales involved it may be d

In and academic pursuit there are always heated debates and disagreements. The debate process is part of the formulation of ideas. It doesn't work the same way as in the corporate world, where you need to have everyone work as a cog in a machine. Academics always have strong views on certain things. Its probably a case of some of the team being overly excited, some being more reserved. In the end most of them will reach consensus based on data analysis. Its part of progress.

Why is this a troll? We've already known that there are a multitude of planets, even earth sized ones. This is really non-news until 1) it is confirmed and 2) they determine whether these are earth sized or earth like.

Kepler needs 3 transits to confirm a planet, so given that it's only been up there since March 7, 2009 any planet around the same distance as earth will only have had 2 transits max.

It's exciting that there are so many candidates but I guess NASA doesn't want the embarrassment of getting everyone all excited then having to hugely backtrack on the number if some turn out to be something else.

No, this is wrong. Where did you learn your orbital mechanics? There's another major factor in the orbit time of satellites: the mass of the star. The more massive the star a planet orbits, the faster its period will be for a given distance.

It's really sad that a discussion about the possible detection of Earth-sized planets around other stars is dressed up in "it's our data and we want to publish first" and stuff like that.Humanity will, one day, pay dearly the fact that scientists are forced to fight for resources...

Anyway, this is interesting news. If computers were considered "the revenge of the nerds", I'm curious what the next few years will be called.

Well if those same scientists would get nuclear fusion and energy-matter conversion working, then we'd have unlimited resources and they wouldn't have to fight over them anymore. So really, it's their own fault for being lazy.

Publishing by press release is a great advantage in the short term, and most scientists won't be missing that lost integrity till later (if at all). These guys don't have to fight for resources -- they choose to. It's a disgrace.

Humanity will, one day, pay dearly the fact that scientists are forced to fight for resources...

Quite the opposite. Given that we have finite resources, the competition amongst scientific groups helps to assure, at least to some degree, that those resources are deployed in the most productive manner.

thank you.Scientists that are also good sailsmen are rewarded. Things are moving along so and so, but not very well: there are millions of people starving because research into genetically modified foods is expensive and you have to worry about patents. And medical research is also expensive and you can run into patents. And so on.OK, maybe I'm exagerating a bit, but when you think about it, many researchers are forced to hold on to secrets because they're worried about getting funding. And, as this comment

By "Earth" like they mean rocky, as opposed to gas giants like Jupiter and Saturn.In this solar system we have Venus - very similar in size to earth and made of rock. However it in no way could be described as habitable by even the toughest forms of life found here.

Theres an article in this months SciAm,(by the same guys, referring to 'super-earths' Rocky planets twice the size of earth or more. They could have life if they were at the right distance from their star, but so far we have only been able to de

And how long before we're mining the crap out of these planets to get our un-obtainium? BTW: The one thing that bothered me most in Avatar was that, while they mentioned it takes 6-years to get to Pandora, they never mention how long it took to discover Pandora. That's a lot of Galaxy to look at.

My prediction is that somehow, we're going to discover, within the next 20 years, something that can be confirmed as "earth-like" in that it appears to have atmosphere and water (from what we can see, being tens of

Don't count on any multi-national rush to visit some random Earth-like planet in our relative stellar neighbourhood; most of them will be way beyond reach.

We will start with absolutely closest stars first, really nvm if there seems to be a habitable planet or not. "And then for the next 300 years" (or so) the small unmanned probe will be en route before even getting there (and hopefully done in a way similar to this concept [wikipedia.org], even if with less advanced tech, to be somewhat capable of mass production & la

One would imagine that if we had figured such things out as cryostasis, interstellar transport, highly advanced cloning and mental transmission (especially that one) that we'd probably have made some advancements in astronomical observation as well. I was more bothered that with all that we couldn't get some metal out the ground without essentially using 20th century strip mining.

They didn't have to discover Pandora. It is in the Alpha Centauri system, 4.37 LY from Earth. This solar system is unique in that it is our closest neighbor by quite a bit, and would thus be the logical first interstellar destination.

You must qualify it a bit better - there's no such thing as "Centauri system" - "...Centauri" is a moniker of stars in the constellation of Centaurus; only few of them quite close. Or probably the closest, as is the case with Proxima Centauri.

I'd love to believe it, but I don't. Yes, there may be vast numbers of solar systems containing rocky planets in approximately the right orbits. But "habitable?" That's a big stretch. I suspect what we'll find is more like Niven's "Known Space" series, where the "habitable" planets out there are weird, marginal, and possibly inhabited by hostile things.

They aren't assuming any such thing. They are only looking for life as we know it on Earth, that's why they only look for Earth-like planets. You can't look for other types of life because you wouldn't know where to start or what to look for anyway.

I can't remember the name of the story, but Isaac Asimov wrote a short story about a Jupiter-sized planet with life that an Earth ship crash lands on (jilling its passengers and destroying the ship, of course), and he held a PhD in biochemistry.

OTOH he did write about thiotimoline, which dissolves before it hits the water...